Alien microorganisms - need reference material for mod

[shynung]

For life "as we know it" it makes sense, but we have no rule book to say that ours is the only possible starting point in all the universe.

Exactly. There is a possibility that there exists some form of life out there that's so strange, we wouldn't even recognize them as life in the first sight.

If life itself began purely by chance, then its chemical composition would depend on what's available on its planet, along with physical conditions and characteristics of the planet's environment. Whatever lived there would adapt to the conditions the planet itself had, along with the challenges it presents. For example, if a planet close to its parent star (Moho) happened to have life somehow, the aliens there would be highly resistant to heat and radiation, or even use it as their primary energy source. Conversely, for far-away planets like Eeloo, life there must adapt to very cold temperatures, and have very efficient metabolism, since energy would be scarce.

The only way that life from one planet to another could be related (seemingly evolved from the same source) is Panspermia, i.e. by asteroids. Asteroids that may be remnants of a once-lively planet that broke apart, carrying inside it frozen microorganism from what was left of its biosphere. If these asteroids happened to collide into a planet suitable for the life within in to survive, then life on that planet could begin from that moment.

[KerikBalm]

"Temperature, light, pressure, moisture, etc"

You still have not provided any examples beyond the commonly accepted limits

[vger]

"Temperature, light, pressure, moisture, etc"

You still have not provided any examples beyond the commonly accepted limits

Kay, you win. Feel good about yourself. I'm not here to get into petty 'Yahoo Comment' arguments about semantics.

Edited March 28, 2014 by vger

[shynung]

"Temperature, light, pressure, moisture, etc"

You still have not provided any examples beyond the commonly accepted limits

Because we don't have any. We haven't seen any. All the life we have seen exists on Earth. If one were to obtain specimens that can actually live beyond commonly accepted limits, one would have to find an actual living extraterrestrial lifeform that lives in conditions beyond our limits. So far, we haven't found any.

[vger]

Because we don't have any. We haven't seen any. All the life we have seen exists on Earth. If one were to obtain specimens that can actually live beyond commonly accepted limits, one would have to find an actual living extraterrestrial lifeform that lives in conditions beyond our limits. So far, we haven't found any.

Granted. The only point I was making is that we shouldn't assume such limits. And instead the discussion turned to "what is a commonly accepted limit?" That, unfortunately, is overly complex, because it doesn't just encompass what the scientific community says, but also the media's interpretation of that, and in-turn, society's interpretation.

[Kryten]

Granted. The only point I was making is that we shouldn't assume such limits. And instead the discussion turned to "what is a commonly accepted limit?" That, unfortunately, is overly complex, because it doesn't just encompass what the scientific community says, but also the media's interpretation of that, and in-turn, society's interpretation.

This isn't social studies, this is a scientific question. If 'the media' 's interpretation differs from the scientific interpretation, it doesn't mean anything other than that the media has messed up a bit of science reporting yet again.

[vger]

This isn't social studies, this is a scientific question. If 'the media' 's interpretation differs from the scientific interpretation, it doesn't mean anything other than that the media has messed up a bit of science reporting yet again.

Had I meant "scientifically-accepted," I would have said that. And the topic is a mod that is speculative (since we haven't actually found life on another world yet). To involve the discovery of otherworldly life means we're delving into the unknown. I can't state this any more plainly than, "Consider allowing the unknown to be different from the known."

[KerikBalm]

Well, we can speculate, as in the wikipedia link, on other solvents, other types of chemistries, etc.

You made a specific claim about life forms we had already identified, and that is what I have an issue with.

I have no problem with speculating about life that uses ammonium or methane as the solvent, for example

[vger]

Well, we can speculate, as in the wikipedia link, on other solvents, other types of chemistries, etc.

You made a specific claim about life forms we had already identified, and that is what I have an issue with.

I have no problem with speculating about life that uses ammonium or methane as the solvent, for example

Fair enough. Maybe my big mistake was saying "definition of life" without putting a time stamp on it. The definition has been stretched a few times as newly discovered lifeforms push the envelope. The best example of this that I can think of is light, which was once considered to be necessary for all life on Earth. Discoveries of creatures that live in pitch-black caves or around undersea vents gave concept a swift kick in the pants.

[Kryten]

That's complete nonsense. We've known about lithotrophs for a lot longer than we've known about deep-sea vents. Some of them simply live in soil.

[vger]

That's complete nonsense. We've known about lithotrophs for a lot longer than we've known about deep-sea vents. Some of them simply live in soil.

So what are you picking apart then? That science once believed light was necessary? Or that you don't like the example?

And go tell it to NASA while you're at it. http://science1.nasa.gov/science-news/science-at-nasa/2001/ast13apr_1/

[Kryten]

So what are you picking apart then?

That you're not addressing science, you're addressing the pop-culture caricature of science. I should probably say now, before you start waffling on about light or pressure any more, that the actual requirements (or so 'science believes') for living organisms are;

1) An oxidised species to act as a terminal electron acceptor

2) A source of energy; either complex carbon(/silicon), an electrochemical gradient, or radiation

3) A source of carbon to produce various organic molecules required for life. Hypothetically silicon could do instead, but no other molecule is likely to be versatile enough

4) Water, or hypothetically other solvents

5) An environment where the various molecules would be stable. This would depend on the exact molecules utilised.

[vger]

That you're not addressing science, you're addressing the pop-culture caricature of science.

This pop-culture caricature of science was even taught to me in gradeschool. But you know what? Not worth it. Carve a notch into your keyboard and cry victory. I've got better things to do than play the intellectual equivalent of two buck ramming their heads together to impress females.

Edited March 28, 2014 by vger

[Kryten]

That 'nobody expected creatures to be able to survive without light' is simply one of the factoids that gets regurgitated in textbooks and popular science articles without anyone checking it. It's like 'the basic tastes are mapped to different parts of the tongue', or 'nobody could explain how blackbody radiation wasn't of infinte power before quantum physics'.

[Sidneyia]

Why is so important light? There are many sources of radiation that are not the sun. It does not matter the wavelength if you have a mechanism to extract electrons from it. And… an organism can get electrons from compounds, not necessary light. I don’t want to argue, just to know: why light?

[KerikBalm]

Light isn't needed, but it is a very abundant energy source.

Its also worth noting that we cannot resolve extra-solar moons. So we can't see anything that may be warmed by tidal flexing.

We can't deterine core composition, so we don't know if a planet has a hot core, kept warm over long periods by radioactive decay.

The only energy source we can be sure of at the distances involved, is light.

We can see the "parent" star. We can't see the rest of it.

So naturally, that is where we look.

I would very much like for more focused missions to be sent to mars, and missions to be sent to Europa/Enceladus.

I have a suspicion that we will find both to be quite sterile (or at least lacking alien life*)- yet potentially habitable.

The conditions neccessary for life to start, are not the same as the conditions that life can survive in.

I can't help but look at mars, and think... where is all the evidence of life?

Its hard to look at this map, and not think that Mars had an ocean:

http://upload.wikimedia.org/wikipedia/en/1/1d/Mars_Map.JPG

Or you can look at pictures like this:

http://upload.wikimedia.org/wikipedia/en/9/94/Eberswalde_delta_plain25.jpg

Curiosity came across a streambed that was flowing long enough to have pebbles rounded by erosion

Numerous sedimentary rock formations have been found

Water was flowing, there were large amounts of it, no question.

Rather old craters in the martian highlands still appear crisp

http://en.wikipedia.org/wiki/Hesperian

- from the time period when wars was drying up, but still seems to have had standing water

Even old riverbeds are still there... so it seems likely that erosion isn't so much that fossiles wouldn't still be around.

http://en.wikipedia.org/wiki/Geology_of_Mars#Inverted_relief

Some of those riverbeds, do however seem to have been affected significantly by erosion - in that apparentyl everything around them eroded, but they remained resistant to erosion, due to the clays and such being cemented together by exposure to water.

Our rovers have encountered numerous places where water was obviously present in the past.

Now... I'm not expectng us to find some fossil fish like thing, even if they were there, 3 rovers could easily miss signs as rare as those.

If one looks at old seabeds and such on earth, the signs of life are easy to see.

Before the cambrian explosion, microbial mats and stromatolites were everywhere.

http://en.wikipedia.org/wiki/Microbial_mat

http://upload.wikimedia.org/wikipedia/commons/9/92/Runzelmarken.jpg

Now stromatolites and microbial mats are only in a few places:

http://upload.wikimedia.org/wikipedia/commons/1/1b/Stromatolites_in_Sharkbay.jpg

http://en.wikipedia.org/wiki/Microbially_induced_sedimentary_structure

- because more complex organisms eat them

And then there are the old banded iron formations

http://en.wikipedia.org/wiki/Banded_iron_formation

If photosynthesis ever evolved on mars, given that no higher organisms would be around to disturb them (ie direct consumption burrowing action, covering them and blocking access to resources, etc), then basically everywhere that had standing water should have been covered with a microbial mat or stromatolites....

and conditions on mars are such that there isn't much appreciable erosion...

Where are the banded iron formations?

Where are the stromatolites, where are the fossilized microbial matts?

If our rovers are looking at ancient lakebeds, assuming no higher organisms evolved that ate mats of cyanobacteria like organisms, and the lakebeds were habitable all the way up to the point that they started drying out, if photosynthesizing bacteria were there, it should be obvious.

Photosynthesis evolved very quickly on earth, and it would be strongly selected for.... so I'd guess the same would be true on mars if it had life.

Yet I still have an idea... what if those "inverted relief" features aren't simply clays cemented together... what if the feature that makes them resistant to erosion... is that the riverbeds and deltas were covered in a massive microbial mats, which are now fossilized and at the top of these inverted relief formations?

These same microbial mats are what seem to have preserved almost all the fossils of pre-cambrian multicellular life. One explanation for the disappearance of fossils of almost all the precambrian multicellular life in the cabrian and higher, is that the microbial mats were gone, and thus the main method by which these fossils were preserved is also gone.

If it were up to me, we'd send a rover to go investigate an inverted relief formation... say in an old delta.

If we don't find fossilized microbial mats there, we'd stop looking for life, and conclude that the requirements for conditions to support life are much less stringient than the requirements for conditions to start life.